The present invention relates to a potentiometer, and more particularly, to a potentiometer which generates an electric signal corresponding to a shaft rotation amount.
A potentiometer is used when an electric signal indicating the amount of displacement of an object is required. The potentiometer has a shaft which rotates by an external force and a converter which converts a rotation amount of the shaft to an electric signal.
In a potentiometer using a slide resistor for conversion of a rotation amount to an electric signal, as abrasion of a slide part degrades performance and operational stability with time, a non-contact type potentiometer is employed to avoid these inconveniences.
A non-contact type potentiometer utilizing magnetism is known. The potentiometer of this type has a magnet attached to an end of a shaft, and a sensor to detect a magnetic flux of the magnet as an electric signal. As the sensor, a Hall device or an inductance device is used (for example, see Patent Documents 1 and 2 respectively.)
As a potentiometer in which the amount of plural shaft rotations is converted to an electric signal in a non-contact manner, known is a potentiometer in which a screw stock to linearly move in correspondence with shaft rotation is provided inside of the shaft and the position of the end of the screw stock is magnetically detected. (for example, see Patent Document 3).
[Patent Document 1] U.S. Pat. No. 4,395,695 (column 2-4, FIGS. 1-3)
[Patent Document 2] U.S. Pat. No. 3,988,710 (column 1-3, FIGS. 1-2)
[Patent Document 2] U.S. Pat. No. 6,411,082 (column 2-3, FIG. 1)
In the constructions described in Patent Documents 1 and 2, merely a rotation amount for one or smaller shaft rotation is detected. Further, the resolution of rotation amount detection is low. In the construction described in Patent Document 3, a rotation amount for plural shaft rotations can be detected, however, the maximum rotation amount is limited.